1. Field of the Invention
The present invention relates to a synthetic or overall control system or apparatus which can be applied to a diversified or sophisticated motor vehicle or automobile system. More particularly, the invention is concerned with a synthetic automobile control system which has flexibility or is expandable in application for a plurality of different types of automobiles for synthetic control thereof with high efficiency and improved performance.
2. Description of Related Art
Electronic control apparatuses developed heretofore for application to motor vehicle systems or automobile systems, include an engine control apparatus, an automatic transmission (AT) control apparatus, a constant-speed cruising control apparatus and so forth. In this conjunction, it should however be noted that these control apparatuses are designed for controlling various actuators of the automobile independent of one another.
Consequently, the various control apparatuses mentioned above require respective sensors (such as rotation speed or RPM sensor, a water temperature sensor, a throttle opening degree detecting sensor and others) for arithmetically determining corresponding control quantities on the basis of various sensor output signals indicating operation states of the automobile, to thereby operate or drive the associated actuators such as a throttle actuator, an ignition unit, an automatic transmission (AT) speed-shift solenoid, a fuel injector and others.
In recent years, however, a trend has arisen for developing a synthetic automobile control system which allows data transfer or communication to be effected freely among different arithmetic control units and actuator driving units incorporated in an automobile system with a view to realizing synthetically enhanced or sophisticated control thereof. As a typical example of this sort of synthetic automobile control system, there may be mentioned, by way of example, a system disclosed in Japanese Unexamined Patent Application Publication No. 95659/1995 (JP-A-7-95659).
The synthetic control system described in the publication mentioned above is composed of an input/output unit for processing a plurality of sensor signals and for driving a plurality of actuators, an arithmetic unit for performing arithmetic operations or processes in accordance with the control data for the individual actuators on the basis of the various sensor signals, and an interface means for coupling the arithmetic unit with the input/output unit, for realizing flexible and easy adaptation to the automobile systems which become diversified or more and more sophisticated.
For a better understanding of the present invention, a description will first be made in some detail of the background technique.
FIG. 28 is a schematic diagram showing a major portion of a conventional synthetic automobile control system known heretofore such as disclosed in Japanese Unexamined Patent Application Publication No. 95659/1995 JP-A-7-95659 on the presumption that a single or an integrated input/output means is provided, and FIG. 29 is a schematic diagram showing another conventional synthetic automobile control system in which an input unit and an output unit are provided separately from each other.
Now, referring to FIG. 28, an input/output unit 102 constituting an input/output means is connected to sensors 104 and actuators 105 and is capable of processing a plurality of input/output signals (sensor signals and actuator driving signals).
On the other hand, an arithmetic unit 101 constituting an arithmetic means performs arithmetic operations involved in controlling an automobile by using the input signals supplied from the sensors 104 after having been processed by the input/output unit 102 to thereby control the actuators 105 via the input/output unit 102. On the other hand, an interface means 103 is constituted by a multiplex communication means for interconnecting the arithmetic unit 101 and the input/output unit 102 with each other through the medium of multiplex communication channels or equipment.
On the other hand, in the system in FIG. 29, an input unit 202 constituting an input means is connected to a plurality of sensors 104 and adapted to process the input signals supplied from the individual sensors 104, while an output unit 203 constituting an output means is connected to actuators 105 and adapted to drive a plurality of actuators 105 on the basis of control quantities determined by the arithmetic unit 101.
More specifically, the arithmetic unit 101 is so programmed as to execute arithmetic operations for controlling the automobile system by using the sensor signals processed by the input unit 202 to thereby drive the actuators 105 via the output unit 203 in accordance with data resulting from the arithmetic operations. The interface means 103 constituted by a multiplex communication means connects the arithmetic unit 101 with the input unit 202 and the output unit 203 by utilizing a multiplex communication facility provided by the interface means 103.
As is apparent from the foregoing, in the case of the synthetic automobile control system known heretofore, the arithmetic means (i.e., the arithmetic unit 101), the input/output processing means (i.e., the input/output unit 102 or the input unit 202 and the output unit 203) are provided independently from one another and interconnected via the interface means 103.
Thus, for a diversity of automobile systems, the input/output signal processing (performed by the input/output unit 102 or the input unit 202 and the output unit 203) and the arithmetic processing (performed by the arithmetic unit 101) can be realized with high efficiency by using one input/output unit 102 or a plurality of input/output processing means (i.e., the input unit 202 and the output unit 203) together with the arithmetic means (i.e., the arithmetic unit 101).
In this conjunction, it is noted that the standardized input/output means (i.e., the input/output unit 102 or the input unit 202 and the output unit 203) is implemented in such a structure as to be capable of performing a plurality of input/output processings.
Accordingly, even when an automobile system which requires a large number of input/output processings, there arises substantially no need for increasing excessively amount of hardware. Besides, in the state where the hardware parts are disposed physically close to one another, it is possible to perform the input/output operations for the sensor signals and the actuator driving signals with high efficiency while sparing wire harnesses.
Next, the description will turn to an ignition control operation of the conventional synthetic automobile control system.
FIG. 30 is a timing chart for illustrating an ignition timing control operation of the arithmetic unit 101 and the input/output unit 102 implemented in an integrated structure and having a knock (or knocking) suppressing function. In the figure, a pulse signal Ne is one of various sensor signals outputted from the sensors 104 and represents an engine rotation number or speed (rpm).
A crank angle .alpha..degree. indicated by the pulse signal Ne may be set at an angular position preceding to a top dead center by 80.degree. (this crank angle position will be referred to as the crank angle position BTDC 80.degree., while a crank angle .beta..degree. may be set, for example, at a position preceding to the top dead center by 10.degree. (also referred to as the crank angle position BTDC 10.degree.). Further, a main period T.sub.0 represents a period of a main processing routine executed by the arithmetic unit 101.
More specifically, there are illustrated in FIG. 30 relations among a timing for arithmetically determining a basic ignition timing, a knock correcting timing determined through an interrupt processing executed at every crank angle .alpha..degree. indicated by the pulse signal Ne and a power transistor driving signal D2 for an ignition-dedicated power transistor included in the actuators 105.
Through the main processing routine executed by the arithmetic unit 101, the basic ignition timing is arithmetically determined at a timing t.sub.b during every main period T.sub.0, while a knock correcting quantity is arithmetically determined at every timing t.sub.c corresponding to every crank angle .alpha..degree. indicated by the pulse signal Ne.
The knock correcting processing (i.e., the ignition-dedicated power transistor driving processing) is executed at a timing t.sub.k corresponding to the crank angle .alpha..degree. indicated by the pulse signal Ne. In other words, the basic ignition timing is corrected by the knock correcting quantity determined arithmetically at the timing t.sub.c corresponding to the crank angle .alpha..degree. in the preceding main period, whereby the ignition-dedicated power transistor is driven at the corrected basic ignition timing.
In this manner, when the ignition timing is arithmetically determined, the arithmetic unit 101 performs knock correction at the timing t.sub.k corresponding to the crank angle .alpha..degree. indicated by the pulse signal Ne to thereby send out the ignition timing data to the input/output unit 102. In that case, because the knock correction processing is executed at every pulse (.alpha..degree.) of the pulse signal Ne, a lag or delay in the transmission of the ignition timing data will exert an adverse influence on the ignition control which should intrinsically be performed without any appreciable delay.
Besides, in the conventional synthetic automobile control system of the structure in which the output circuit for driving the actuators 105 and the input circuit for processing the sensor signals from the sensors 104 are incorporated in one and the same input/output unit 102 which constitutes the input/output processing means, as shown in FIG. 28, a great difficulty will be encountered in coping with cross-talk noise between the output circuit and the input circuit. In other words, influence of noise superposed on the intrinsic signals can not be eliminated, giving rise to a problem. Additionally, when a fault occurs in the arithmetic unit 101 or the interface means 103, there arises a serious problem that the control system as a whole is rendered inoperative.
On the other hand, in the case of the synthetic automobile control system equipped with a plurality of input/output processing means, the problem of cross-talk noise between the input unit 202 and the output unit 203 can certainly be mitigated because they are provided discretely or independent of each other. However, when a fault takes place in the arithmetic unit 101, the interface means 103 or the input unit 202, there will undesirably arise a great possibility that the whole control system will become impotent in carrying out the control operations as required, involving another problem.
Additionally, in the synthetic automobile control system shown in FIG. 28 (or FIG. 29), the actuators 105 are driven through the multiplex communication effectuated by the interface means 103 interposed between the arithmetic unit 101 and the input/output unit 102 (or between the arithmetic unit, the input unit 202 and the output unit 203). Thus, there is required signal transmission from the input/output unit 102 (or input unit 202) to the arithmetic unit 101 and data transmission from the arithmetic unit 101 to the input/output unit 102 (or the output unit 203), which means that a time lag due to the bidirectional communication is no more negligible. Besides, the possibility of the occurrence of a communication error will increase, to another disadvantage. In particular, when the data to be processed at a highest rate or instantaneously, such as the data for the ignition control, is transferred through the communication, a time lag involved in the communication provides a great obstacle to the ignition control, incurring a very serious problem.
Furthermore, when the ignition timing is controlled for the purpose of suppressing the knock event, the knock correcting timing is validated at every crank angle .alpha..degree.. Consequently, a time lag occurs in the communication, affecting adversely the ignition control which requires instantaneous effectuation without any appreciable delay.